The present invention relates to an inspection system for sampling and determining the presence of certain substances, such as residues of contaminants within containers such as glass or plastic bottles. More specifically, the present invention relates to an improved sampling and analyzing system and method for determining the presence of substances such as residues of contaminants, as in containers such as beverage bottles rapidly moving along a conveyor past a test station in a container sorting system.
In many industries, including the beverage industry, products are packaged in containers which are returned after use, washed and refilled. Typically refillable containers, such as beverage bottles, are made of glass which can be easily cleaned. These containers are washed and then inspected for the presence of foreign matter.
Glass containers have the disadvantage of being fragile and, in larger volumes, of being relatively heavy. Accordingly, it is highly desirable to use plastic containers because they are less fragile and lighter than glass containers of the same volume. However, plastic materials tend to absorb a variety of organic compounds which may later be desorbed into the product thereby potentially adversely affecting the quality of the product packaged in the container. Examples of such organic compounds are nitrogen containing compounds such as ammonia, organic nitrogen compounds, and hydrocarbons including gasoline and various cleaning fluids.
The aforementioned application Ser. No. 07/890,863 discloses a system and method for detecting the presence of these nitrogen containing and hydrocarbon compounds using a chemiluminescence analyzer. That system and method works quite well, but improvements are desirable to overcome interferences which may occasionally cause difficulties in achieving desired sensitivity and accuracy of detection. Such interferences result from background signals which may mask detection of low levels of certain compounds and whose variation with time may also result in false positives (and thus unwarranted rejection of uncontaminated containers). Accordingly, a need in the art exists for a chemiluminescence analyzer with improved accuracy and sensitivity.